Rapid development of mobile Internet makes data services take up a predominant proportion. A modem plays an increasingly important role and thus has an increasingly important place in a mobile phone. The modem is used for converting data to be sent into a radio frequency signal, converting a device signal into data to be processed, processing signaling of an Access Stratum (AS) and a Non-Access Stratum (NAS), and interfacing with an Application Processor (AP). When a mobile network environment in which the mobile phone resides is very complicated, the mobile phone may be frequently switched between different communication systems, and a network communication function of the modem may frequently become abnormal in the process of switching between the communication systems, thus resulting in that the mobile phone cannot be normally networked for communication.